In communication systems, wherein a Mobile Subscriber MS is on the move, the frequency varies according to Doppler effect, as it communicates with a Base Station BS.
It is desired to estimate and correct the Doppler effect, and other effects as well which result in frequency error—and reduce communications systems performance.
In many communication protocols, such as 802.16e or WiMAX, there are several frequency carriers and/or subcarriers, at some frequencies and distanced apart.
In S-WiMAX and some other communication protocols and systems, the carrier spacing may be reduced, such as about 2 KHz. In such cases the expected Doppler shift (e.g. 200 Hz) might be too large to be left uncompensated and may affect performance, thus it may be required to compensate for this effect. Doppler shifts may be compensated at the MS and/or at the BS.